Ingestive behavior of lambs fed diets supplemented with slow-release urea microencapsulated into carnauba wax and amino acids blend

Abstract

The rapid degradation of conventional urea in the rumen can result in excessive ammonia production, impairing animal performance and posing toxicity risks. To overcome this, controlled-release urea (SRU) has been developed as a cost-effective alternative that gradually supplies nitrogen, aligning more effectively with the availability of fermentable energy and enhancing microbial protein synthesis. Combined with amino acids such as lysine and methionine, this strategy further improves nitrogen-energy synchrony, promoting balanced and efficient ruminant nutrition. This study evaluated the ingestive behavior of 40 male lambs of undefined breed, averaging 18.3 ± 3.0 kg in body weight and approximately four months of age. The animals were allocated to five dietary treatments in a completely randomized design with eight replicates. Treatments included: a control diet (no SRU or amino acids); 4% SRU; 4% SRU + 1.5% lysine (SRU + L); 4% SRU + 1.5% methionine (SRU + M); and 4% SRU + 1.5% lysine + 1.5% methionine (SRU + L + M). SRU was microencapsulated using the fusion-emulsification method with carnauba wax (Copernicia prunifera) as the encapsulating agent. Lambs were fed for 60 days on total mixed rations containing 30% roughage (a mixed silage of Sorghum bicolor and Panicum maximum) and 70% concentrate (ground corn, soybean meal, mineral mix, and respective treatments). Eating (P = 0.011) and rumination (P = 0.038) time differed significantly across treatments. Control and SRU-only diets resulted in shorter eating (2 h) and longer rumination (7 h 30 min) times, while SRU + M and SRU + L + M increased feeding duration (3 h 30 min) and reduced rumination (6 h 20 min). Idling time was not affected. SRU, when associated with amino acids, increases rumination time and reduces eating time, which may improve the use of fibrous diets and ruminal conditions.